In accordance with the recent development of electrical engineering, electronic apparatuses are miniaturized, become highly performable, and become portable. Therefore, electrochemical devices used as a power source for electronic apparatuses become more compact and less-weighted and demonstrate higher performance. Especially, chargeable secondary battery is increasingly used. The conventionally used secondary battery is, for example, NiCd battery and nickel hydride battery. More recently, secondary battery using a non-aqueous electrolyte such as lithium secondary battery and lithium ion secondary battery is used because it has higher energy density. Meanwhile it is tried to use electric double layer capacitor as a power source because of its high output.
In a conventional technique, one example of structures of secondary battery using a non-aqueous electrolyte and having a large capacity and a high energy density is a cylindrical structure as illustrated in FIG. 11. As illustrated, a winding element formed by winding a pair of strip-like electrodes, i.e. specifically a positive electrode 2 made by forming layers including a positive electrode activating agent on both sides of a metallic collector and a negative electrode 3 made by forming layers including a negative electrode activating agent on both sides of a metallic collector, interposing strip-like separators 4, 4′ therebetween, is accommodated in a metallic case in a form of bottomed cylinder and subjected to impregnation with an electrolyte. Thereafter, collecting leads 6, 6′ drawn out of the positive electrode 2 and the negative electrode 3 are respectively connected to electrode terminals 9, 9′, formed in an electrically insulative sealing lid 8, and the sealing lid is engaged with the metallic case 5.
As used above and throughout the remainder of the specification, “strip-like” is to be understood to mean “strip shaped.”
In the case of the above-described electrochemical device, the production time becomes long because a step of processing the leads is onerous.
Further, it is necessary to provide an additional space for accommodating the collecting leads in the case, whereby the winding element becomes small as much. Therefore, the volume density per a unit volume of the case was inevitably low. Further, because the electrolyte is injected after the winding element is accommodated in the case and the opening portion of the case is sealed by the sealing lid, a substantial time is necessary to inject the electrolyte. Further, an electrochemical device having a smaller internal resistance is desired.
An object of the present invention is to provide an electrochemical device, wherein the production time is short, the capacity density per a unit volume is high, an electrolyte is injected thereinto in a short time, and the internal resistance is small.